1. Field of the Invention
The invention relates to notch radiator elements. In particular, the invention relates to high frequency notch radiator devices employing circuit elements in printed and machined arrangements for use in antenna arrays.
2. Description of the Prior Art
Known notch type radiator elements such as element 10 in FIG. 1 comprise a 50 ohm stripline 12 and a notch antenna 14. A double slot line tapered launch or aperture 16 has a narrow 50 ohm feed end 18 fed by the stripline 12 and a wide 376 ohm radiating aperture 20 which matches the air. The stripline 12 and the feed end 18 have respective quarter wavelength extensions 22 and 24 which form terminations for each. In the arrangement shown, the stripline 12 is buried within a dielectric substrate 26 and the aperture 16 is formed of etched metallized films on opposite sides of the substrate 26.
The radiator 10 is designed to transmit or receive RF signals. In the transmission mode, a signal carried by the stripline 12 sets up an electric field in the feed end 18 of the aperture 16. The electric field radiates outwardly and couples the signal to the air or other medium at the aperture end 20. Incoming signals are likewise coupled to the aperture 20 for ultimately producing an electric field in the stripline 12. The tapered wall 17 of the aperture 20 provides a transition between the standard 50 ohm stripline 12 and the 376 ohm (nominal) atmosphere. In known arrangements, a plurality of such elements are manufactured in continuous strip. Sometimes stray or extraneous fields are produced as a result of coupling inefficiencies and the like between the stripline 12 and the aperture 16.
Adjacent elements are electrically isolated for suppressing the stray fields by means of metallic shields 28 formed in vias 30 in the substrate 26. The shields 28 are in electrical contact with the metallized film forming the aperture 16 as shown.
In the known arrangements, difficulties have been encountered in obtaining desired bandwidth and impedance matching. Processing difficulties including shrinkage of the dielectric during manufacture results in some cumulative non-uniformities in arrangements employing an elongated dielectric board containing many elements. In addition, cross coupling between adjacent elements occurs as a result of signal leakage through the metallic shields 28.